Non-caking sodium tripolyphosphate



United States Patent U.S. Cl. 23106 2 Claims ABSTRACT OF THE DISCLOSUREA compacted sodium tripolyphosphate having a specified density andparticle size and having distributed on it 2.5 to 7% of water isprovided. The presence of the specified amount of water on this kind ofsodium tripolyphosphate renders it capable of dissolving readily inwater without caking.

This is a division of application Ser. No. 462,082 filed June 7, 1965,now U.S. Patent 3,360,469.

This invention relates to dry-mixed built detergent compositions, andparticularly to such compositions which contain as an essentialcomponent fast-hydrating, dense sodium tripolyphosphate builder in aform in which it is readily soluble without caking under adversedissolving conditions.

Built detergent compositions useful in automatic washing machines,dish-washers, sanitizing applications, bleaching applications and thelike are available in tablet, granular and liquid forms. The tablet andgranular forms have particular advantage because they are easily handledand stored as compared .with the liquid materials, and because with themit is not necessary to ship and store water as is the case with liquidcompositions. This invention is concerned with the dry compositions,namely the tablet and granular varieties.

These dry compositions generally contain sodium tripolyphosphate as abuilder and any or all of an anionic or nonionic surfactant, ananti-corrosion agent such as sodium silicate, a chlorinated cyanuriccompound such as trichlorocyanuric acid, dichlorocyanuric acid or a saltof dichlorocyanuric acid, chloroin ated trisodium phosphate, an alkalicarbonate and an inert inorganic filler such as sodium sulfate, sodiumchloride, sodium orthophosphate and the like. The surfactant and thesodium tripolyphosphate are the principal cleaning components, while thesodium silicate prevents the alkaline detergent from attacking metallicparts of washing machines and the like with which it comes into contactwhen dissolved in water in use. The chlorinated cyanuric compound servesas a sanitizing and bleaching agent and the filler is employed as anextender to obtain the desired bulk density and to provide smoothertablets and more uniform compositions. The makeup of the compositionsdepends on the ultimate use to which they will be put.

There are basically two methods of preparing these dry compositions. Onemethod involves forming an aqueous slurry of the sodium tripolyphosphateand other ingredients, while the other method simply involvesdry-blending the ingredients and either using them directly as granularcompositions or tableting them. The dry-blending system has the obviousadvantage of ease of operation in not requiring drying, for examplespray-drying, to provide the final product.

A serious problem is inherent in dry-blending compositions, however,which is not as aggravated in forming the compositions from slurries.Sodium tripolyphosphate,

an essential constituent of these compositions, is erratic in itsdissolving characteristics. Its dissolution in water in end use or insome cases in subsequent processing sometimes is slowed, and thematerial even cakes into insoluble, cohesive masses if entrappedtemporarilyin a piece of cloth, or if not properly agitated, such asmight occur in a washing machine or upon pouring the granularcomposition into a container of water without agitation. Even absentsuch a condition, compositions containing more than about of sodiumtripolyphosphate frequently cake in water. This problem is particularlyaggravated in dry-mixed compositions, whose preparation does not exposethem to water. When the compositions are prepared in water, a tendencyin the sodium tripolyphosphate to give serious trouble in dissolving onuse of the composition, often shows up during preparation of thecomposition.

In an attempt to overcome this unpredictable and serious dissolvingproblem, as well as to provide a dense sodium tripolyphosphate ofregular particle size, H. L. Marschall et al. provided a method ofproducing a sodium tripolyphosphate having -a density of about 1.0 to1.25 g./cc., and a desirable hydration and dissolving rate. Their methodcomprises compacting the sodium tripolyphosphate at a high pressure intoa large, dense mass of the material, and grinding this mass to theproper particle size. This is taught in the Marschall et al. U.S. patentapplication, Ser. No. 289,315, filed June 20, 1963, and assigned to theassignee of this invention, now U.S. Patent No. 3,338,671, issued Aug.29, 1967.

The dense, granular sodium tripolyphosphate provided by Marschall etal., referred to hereinafter as compacted sodium tripolyphosphate, has afaster rate of dissolution in Water under normal conditions, than doessodium tripolyphosphate not :produced by their method. However, it hasnot been found in practice to solve all problems relative to dissolving.While under normal conditions it dissolves in water more readily thandoes non-compacted sodium tripolyphosphate, there are certain adverseconditions, for example when a composition contains on the order of 75or more of sodium tripolyphosphate or when the composition is notagitated when added to water or is temporarily entrapped such as in apiece of clothing in a washing machine or in a dispenser of the kindused for example in a home dishwasher, (which cause it to cake and notdissolve despite its normally fast dissolving characteristic.

It therefore has remained desirable, and it is an object of thisinvention, to provide a sodium tripolyphosphate which not only has afast dissolving rate under normal dissolution conditions, but also whichdissolves readily without caking under adverse conditions.

I have now found it possible to provide an improved form of compactedsodium tripolyphosphate which produces dry-mixed built detergentcompositions which dissolve readily without caking under normal, andalso under adverse, dissolving conditions. The improved compacted sodiumtripolyphosphate of my invention is pro vided by uniformly distributingon a compacted sodium tripolyphosphate containing 0 to 0.7% by weight ofWater, an amount of water to increase the amount of water in thetripolyphosphate to 2.5 to about 7%, and preferably 2.5 to 4%, byweight. This improved material is then dry-mixed in a compositioncontaining by weight about 20 to of my sodium tripolyphosphate and anyor all of 0 to 50% of a water-soluble, non-soap organic syntheticdetergent which may be an anionic or nonionic detergent, about 0.5 to50% of sodium silicate, 0.5 to

' 20% of a chlorocyanuric compound, 0.5 to 50% of chlorinated trisodiumphosphate, 0.5 to 50% of an alkali carbonate and 0.5 to 60% of an inertinorganic filler. The components present in a given composition vary asthe compositions end use varies, and a variety of combinations of theseadded ingredients in practice are used with my improved sodiumtripolyphosphate. These compositions may be granular, in which case theyare produced by simply mixing the components together, or in tabletedform, in which case the granular compositions are tableted underpressure. Throughout the specification and in the claims appendedhereto, reference to compositions as being dry-mixed means compositionswhich are not slurricd or dissolved in a liquid in compounding, andwhich are free-flowing, solid compositions. The 2.5 to 7% of water in myimproved compacted sodium tripolyphosphate obviously does not causecompositions prepared from it to be removed from this dry-mixedcategory.

For some reason which is unknown to me, sodium tripolyphosphate whichhas not been compacted by the process of the Marschall et a1. patentapplication referred to above to produce a uniform sodiumtripolyphosphate product having a density of about 1.0 to 1.25 g./cc.,does not respond to addition of moisture in the above amounts at all inthe same fashion as does the compacted material. It is most surprising,therefore, that it is possible to effect the herein improvement ofdry-mixed built detergent compositions by employing in them compactedsodium tripolyphosphate treated in accordance with my invention.

The improved sodium tripolyphosphate employed in preparing thecompositions of my invention is produced from the Marschall et al.compacted material in accordance with my invention by exposing it to ahumid atmosphere, preferably while the sodium tripolyphosphate is influidized state, by spraying Water into the tripolyphosphate while thelatter is undergoing agitation or the like. The amount of water presentin the sodium tripolyphosphate is analyzed by heating the sodiumtripolyphosphate at 150 C. for one hour and observing the weight lossproduced thereby. Normally the moisture content of the compacted sodiumtripolyphosphate before treating is about to 0.7% depending onconditions encountered in preparing the material and in storing it.

I have found the minimum amount of water required to be present in thecompacted sodium tripolyphosphate to provide a material useful inproviding the herein highly soluble compositions to be quite critical,as shown by a socalled caking test. This test involves placing a -gramsample of the sodium tripolyphosphate in granular form in a porcelaincrucible (Coors No. 2) and carefully adding 6 ml. of distilled water tocompletely cover the tripolyphosphate. The tripolyphosphate is thenprobed gently with a dissecting needle at 10 second intervals, and thetime at which caking (the formation of a hard mass of material) occursis noted.

The dependence on its water content of the ability of compacted,granular sodium tripolyphosphate to withstand caking and the specificityof this property to compacted tripolyphosphate are demonstrated inTables 1 and 2 which follow:

Table 1.Caking time of compacted granular sodium tripolyphosphate[Particle size -+100 mesh, U.S. Standard] Water content, percent: Cakingtime, seconds Anhydrous 10 0.5 10 1 10 2.0 10 2.1 10 2.2 10 2.5 300+ 3.0300+ 4 300+ 5 300+ 7 300+ Table 2.--Caking time of non-compactedgranular sodium tripolyphosphate 1 Water content, percent: Caking time,seconds -20+100 mesh, produced by rotary calcining.

Caking times of on the order of 300 seconds or more are indicative of aproduct which will dissolve readily in use, regardless of the existenceof adverse conditions.

In preparing the dry-mixed, built detergent compositions of myinvention, the principal ingredient, the compacted sodiumtripolyphosphate containing the herein amount of water, is measured intothe detergent formulation in amount sufficient to constitute about 20 toby weight of the composition. Preferably it has a particle size of about16 to mesh with no more than about 20% being 70 mesh.

A surface active agent, which may be either anionic or nonionic, also isdesirable in many compositions. Certain cationic surfactants cannot beemployed because they are incompatible with the compacted sodiumtripolyphosphate. When used the surfactant is added to the mixture inthe amount of about 0.5% to 50% by weight of the composition.

A sodium silicate having an Na O to SiO mole ratio of about 1:1 to about113.2, in amount of about 0.5 to 50% by weight may be included in theformulation also as an anti-corrosion agent and for its building andalkaline properties. The mole ratio of Na O to SiO in the silicatedetermines its alkalinity; as the ratio approaches 1:1 the sodiumsilicate becomes more alkaline. Ratios below 123.2, for example 1:4,dissolve too slowly and are not effective.

Another ingredient which is often useful in these formulations is achlorocyanuric compound, which may be trichlorocyan-uric acid,dichlorocyanuric acid, or the alkali metal or alkaline earth metal saltsof dichlorocyanuric acid, exemplified by sodium dichlorocyanurate,potassium dichlorocyanurate, calcium dichlorocyanurate and the like.These materials, which serve as sanitizing and bleaching agents, aresolids and are available in granular form. When used they generally areemployed in amounts of about 0.5 to 20% by weight. Another usefulchlorinated compound is chlorinated trisodium phosphate which may beused in an amount of 0.5 to 50% as a sanitizing agent.

The alkali carbonates are also useful additives for many formulations.Typical carbonates are sodium sesquicarbonate and sodium carbonate,which are useful in an amount of about 0.5 to 50 Inert inorganic fillersalso may be employed in these compositions. Typical fillers includesodium sulfate, sodium chloride, sodium orthophosphates and the like.Where used they control the bulk density of the composition and improvethe surface appearance and strength of tablets containing them.

In addition, small amounts of auxiliary compounds such as sodiumcarboxyrnethyl cellulose, normally in an amount of 0.2 to 1.5%, foamstabilizers such as lauroyl diethanolarnide, tarnish inhibitors,fluorescent brighteners, perfumes, bacteriostats, coloring matter andthe like may be employed in my compositions. Where it is desired toemploy the compositions as granular mixes they are merely packaged intheir mixed form. Where it is desired to form them into tablets, theyare uniformly mixed and then compressed into tablets. The pressingnormally is carried out at a pressure of on the order of 100 to 350p.s.i., and the finished tablet has a bulk density in the a g f bout .8o .3- "Dhe t lets no ma ly ave strengths (when pressed on edge) of aboutto pounds or more. If the tablets are suitably aged for at least 24hours, they have a strength (when pressed on edge) of up to about 25pounds.

Anionic surface active agents are useful in my formulation in amounts offrom about 0.5% to about 50% by weight. These anionic surface activeagents are non-soap synthetic detergents made up of water-soluble saltsof organic sulfuric reaction products having from about 8 to about 18carbon atoms in the form of a straight-chain or branched chain alkylradical or an acyl radical within the molecular structure and containingsulfuric or sulfoni c acid ester radicals. Typical examples of theseanionic surface active agents are sodium or potassium alkyl benzenesulfonates or sodium or potassium alkyl sulfates or sulfonates in whichthe alkyl group, which may be straight or branched chained, containsfrom about 8 to about 18 carbon atoms, e.g. sodium dodecyl benzenesulfonate, sodium tridecyl benzene sulfonate; the sodium and potassiumalkyl glycerol ether sulfonates, including ethers of higher fattyalcohols derived from. the reduction of coconut oils; the reactionproducts of isethionate; sodium or potassium alkyl sulfonates andsulfates obtained by sulfonation of coconut or tallow fatty alcohols andmixtures of such alkyl sulfates; dialkyl esters of sodium or potassiumsalts of sulfosuccinic acid; sodium or potassium salts of sulfates orsulfonated monoglycerides, e.g. those derived from coconut oil; sodiumor potassium salts of higher fatty alcohol esters of sulfocarboxylicacids, e.g. sodium salt of lauryl alcohol ester of sulfoacetic acid; andother anionic agents set forth in U.S. Patent 2,486,921 issued to Byerlyon Nov. 1, 1949. If desired, the anionic surfactant can be added in theform of a dense, dry head or as a flake admixed with sodium sulfate. Inthis latter case, the sodium sulfate constitutes a portion of the totalsodium sulfate used in making up the entire mixture.

The nonionic surface active agents useful in the present invention arenon-soap synthetic detergents made up of a water solubilizingpolyoxyethylene group in chemical combination with an organichydrophobic compound. Among the hydrophobic compounds which can be usedare polyoxypropylene, the reaction product of propylene oxide andethylene diamine, aliphatic alcohols, etc.

Examples of nonionic synthetic detergents useful in the presentinvention are, condensation products of 6 to 30 moles, and preferably 7to 11 moles, of ethylene oxide with 1 mole of an alkyl phenol containing6 to 12 carbon atoms in the alkyl group; condensation products of 6 to30 moles of ethylene oxide with 1 mole of an aliphatic straight orbranch chained alcohol containing 8 to 18 carbon atoms; condensationproducts of ethylene oxide and the reaction product of propylene oxideand ethylene diamine; nonyl phenol polyethoxy ethanol (commerciallyknown as Triton N series); isooctyl phenol polyethoxy ethanol(commercially known as Triton X series). Another well known group ofnonionic detergents is marketed as Pluronic series. These compounds arethe reaction products obtained by condensing ethylene oxide with ahydrophobic base produced by the condensation of propylene oxide withpropylene glycol, and have. molecular weights on the order of about1800. The addition of polyoxyethylene radicals to the hydrophobic baseincreases the water solubility of the nonionic detergent andconcurrently increases the foaming properties of the detergent inaqueous solution in proportion to the mole ratio of polyoxyethyleneradicals to the hydrophobic base. In general, a surfactant which has amole ratio of 7.5 moles of ethylene oxide per mole of an alkyl phenol,e.g. nonyl phenol, is low-foaming while one with a mole ratio of 10:1foams moderately. The molecular weight of these nonionic syntheticdetergents will range from as low as 800 up to about 11,000.

Nonionic surfactants should be employed in the herein compositions inthe amount of about 0.5 to 15% by weight of the total composition orabove in order for the surfactant to be completely effective. Amountsover 15% should be avoided because the nonionic surfactant tends toexude or oil out of the detergent formulation when it is pressed intotablets. Within the range of 0.5 to 15 the nonionic surfactant giveseffective washing action, and has been found to be effective as a binderfor the remainder of the detergent formulation without oiling out of thepressed tablet.

The following examples are presented by way of illustration of thisinvention only, and are not to be considered as limiting the scopethereof in any way. All amounts are present by weight.

Example 1.Tablets A compacted sodium tripolyphosphate having a densityof 1.2 g./cc. anda particle size of 20+100 mesh was treated with waterby spraying while the sodium tripolyphosphate was being agitated toprovide a material having a water content of 3%. This material wasstirred together with an amount of anionic spray dried beads to providea -10% by weight tripolyphosphate-anionic spray dried bead granularmixture. The beads were composed of 41.9% of sodium tridecyl benzenesulfonate, 0.9% of carboxymethyl cellulose, 36.4% of sodium sulfate,8.2% of sodium metasilicate and 12.6% of sodium chloride. This mixtureof the sodium tripolyphosphate and the beads was then compacted intotablets having a diameter of 1% inches and a thickness of 1 inch, andweighing 50 grams.

A corresponding tablet was prepared in the same Way from compactedsodium tripolyphosphate which had not been provided with the 3% ofwater, but rather was used with its initial amount of 0.5% of water.

The two tablets were placed in one-half inch wire mesh cages placed in afixed position in a top-loading automatic home washing machinecontaining 16 gallons of agitated F. tap water. The tablet containing mywater-treated compacted sodium tripolyphosphate disintegrated in 71seconds and entirely escaped from the cage, while a 9.9 gram core orcake of the tablet containing the compacted sodium tripolyphosphate nottreated in accordance with my invention remained after 5 minutes in thewasher.

The same kind of comparative results was obtained when samplescontaining 78% of sodium tripolyphosphate and the balance the anionicspray dried bead were tested, thus demonstrating that my water treatmentof compacted sodium tripolyphosphate is effective in compositionscontaining both amounts of tripolyphosphate. These amounts are in therange in which sodium tripolyphosphate dissolution is erratic.

Example 2.Tablets Tablets containing 55 parts by weight of sodiumtripolyphosphate and 45 parts of the anionic spray dried beadcomposition used in Example 1 were prepared and tested in the same wayas were the tablets of Example 1. The tablet prepared with myWater-treated compacted sodium tripolyphosphate disintegrated completelyand left the cage in seconds. The tablet prepared with the compactedsodium tripolyphosphate which was not water treated in accordance withmy invention required 167 seconds to disintegrate and leave the cage.

Examples 3 to 6 8 of each composition into an individual beaker contairrtions which are soluble in water without caking under ing one liter ofwater at the indicated temperature. The adverse conditions, comprising agranular compacted composition was permitted to sit in the water for onesodium tripolyphosphate having a density of 1.0 g./cc.

minute before agitation with a magnetically-operated to 1.25 g./cc. andproduced by compacting particles Of stirrer was commenced. The ease ofdispersion was noted. sodium tripolyphosphate at temperatures belowabout The granular compositions normally were of a particle 350 C. toform non-friable, compacted particles folsize to pass through a meshscreen and be retained on lowed by grinding said compacted particles toform a 200 mesh screen, with the individual components varying withinthis range.

TABLE 3.-DISSOLVING PROPERTIES OF GRANULAR FORMULATIONS CONTAININGSODIUM TRIPOLYI-HOS- PHATE \VITH AND \VITHOUT THE \VATER TREATMENT OFTHIS INVENTION Type Laundry detergent Hard surface cleaner Machinedishwashing Hand dishwashing detergent detergent 3 A 4 B 5 C 6 D ExampleN0. (comparative) (comparative) (comparative) (comparative) Composition,wt. percent;

Compacted sodium tripolyphosphate (3% water) 40 28 30 30 compactedsodium t yphosphate (anhydrous) Anionic spray dried beads of Example1... 60 Disodium phosphate Sodium sesquicarbonate. Sodium carbonateSpray dried beads alkyl benzene sulfonate, sodium sulfate) 1. 5 Sodiummetazilicate Sodium dichlorocyanurate Low-foaming nonionic surfactant(polyethoxylated isooctyl phenol with terminal isobutyl groups) 1.5Sodium suliate 30 30 Dissolving properties:

Water temperature, F 120 90 90 140 90 9o Dissolving properties No cakeSoft cake No cake Hard cake No cake Hard cake No cake Hard cak Pursuantto the requirements of the patent statutes, the granular particles, andhaving 2.5 to 7% of water uniprinciple of this invention has beenexplained and eXemformly distributed thereon. plified in a manner sothat it can be readlly practiced by 30 2. The compacted sodiumtripolyphosphate of claim 1 those skilled in the art, suchexemplification lncluding in which 2.5 to 4% of water is present on saidgranular what is considered to represent the best embodiment ofcompacted sodium tripolyphosphate. the invention. However, it should beclearly understood that, within the scope of the appended claims, theinven- 4O References Cited tion may be practiced by those skilled in theart, and UNITED STATES PATENTS having the benefit of this disclosure,otherwise than as specifically described and exemplified herein. 33386718/1967 Marshall at 23106 What is claimed is: 1. A compacted sodiumtripolyphosphate particularly OSCAR R'VERTIZPrlmary Exammer' suited toproviding yi built detergent compose 45 LUTHER A. MARSH, AssistantExaminer.

